Microstructure and giant magnetoresistance of Ag-Co films fabricated by means of an extremely clean sputtering process (comparied with Cu-Co films)

摘要

The influence of impurities in the sputteringatmosphere on the microstructure and giant magnetoresistance(GMR) of Ag_(100-x)Co_x (x=0-62 at percent) thin films wasinvestigated. Ag-Co films were prepared on quartz substrates atroom temperature, varying the purity of the sputtering atmosphereby changing the base pressure, with 10~(-11) Torr for an extremelyclean process (XC-process) and 10~(-7) Torr for a lower-gradeprocess (LG-process). The correlation between the microstructureand the GMR of Ag-Co films after annealing is discussed. It wasfound that (1) the precipitation of Co particles progressed in theas-deposited films, and the degree of supersaturation of the matrixphase in the LG-processed films was higher than that in the XC-processed films; (2) the size of the Co particles precipitated in theas-deposited LG-processed films was larger than that in the XC-processed films, and resulted in a higher MR ratio of the as-deposited LG-processed films than that of the XC-processes onesunder a maximum applied field of 14 kOe; (3) the magnitude ofthe MR ratio in the XC-processes films after annealing above 300deg C was larger than that in the LG-processed ones, apparentlybecause of the homogeneity of the Co particles of the precipitate.